Polarizing plate

ABSTRACT

The present application relates to a polarizing plate and a display device. In the present application, a polarizing plate can be provided, which can be applied to a display device comprising a highly reflective panel to solve disadvantages while maintaining advantages of the device. In the present application, a display device comprising the polarizing plate and the highly reflective panel can also be provided.

TECHNICAL FIELD

This application is a National Stage Entry of International ApplicationNo. PCT/KR2017/001232 filed on Feb. 3, 2017, and claims the benefit ofKorean Application No. 10-2016-0013473 filed on Feb. 3, 2016 and KoreanPatent Application No. 10-2017-0015578 filed on Feb. 3, 2017, all ofwhich are hereby incorporated by reference in their entirety for allpurposes as if fully set forth herein.

The present application relates to a polarizing plate.

BACKGROUND ART

An LCD (liquid crystal display) is a display device using lighttransmittance varying according to arrangement of liquid crystals, whichmay display desired colors and images by controlling transmission oflight emitted from a backlight according to a voltage applied to liquidcrystals and passing it through a color filter.

In a typical LCD, liquid crystals are present between a lower substrateon which a TFT (thin film transistor) is formed and an upper substrateon which a color filter and a BM (black matrix) are formed. Here, thelower substrate is a substrate located closer to the backlight side thanthe two substrates included in the LCD, and the upper substrate is asubstrate present on the viewing side.

In such a general LCD, a reflectance measured at the upper substrateside is generally about 10% at a wavelength of 550 nm.

Recently, an LCD comprising a structure in which the color filter andthe BM are present together with the TFT on the lower substrate otherthan the upper substrate, or in which the BM is absent and the colorfilter exists together with the TFT on the lower substrate is beingdeveloped. Such an LCD has no BM or the like on the upper substrateside, and thus has excellent luminance characteristics. However, sincethe BM or the like is not present on the upper substrate, thereflectance of external light due to the reflection by an electrode orthe like rises, so that a problem that a visual sense, particularly, avisual sense in a black state, of the display is distorted arises.

DISCLOSURE Technical Problem

The present application provides a polarizing plate.

Technical Solution

The present application relates to a polarizing plate. In thisspecification, the term polarizing plate may mean a polarizer, that is,a functional element itself exhibiting a polarization function such as aPVA (poly(vinyl alcohol)-based film, or may mean an element comprisingthe polarizer and other components. Here, the other components includedin the polarizing plate together with the polarizer may be exemplifiedby a polarizer protective film, an optical retardation film, an adhesivelayer, a pressure-sensitive adhesive layer or a low-reflection layer,and the like, but is not limited thereto.

The polarizing plate of the present application is a polarizing platefor a highly reflective panel, that is, a polarizing plate applied to ahighly reflective panel. In the present application, the term highlyreflective panel may mean a display panel having a reflectance (based ona wavelength of 550 nm) of 11% or more, 12% or more, 14% or more, 16% ormore, 18% or more, 20% or more, 21% or more, or 22% or more. Thereflectance (based on a wavelength of 550 nm) of the highly reflectiveliquid crystal panel may be, for example, 30% or less, 28% or less, 26%or less, 24% or less, 22% or less, or 20% or less. The highly reflectivepanel may be a transmissive panel. That is, the highly reflective panelis a panel exhibiting a high reflectance by a unique structure asdescribed below, which may not be a panel in which the reflectance isincreased by separately introducing a reflective plate or the like, suchas known semi-transmissive reflective liquid crystal panels orreflective liquid crystal panels. Thus, in one example, the highlyreflective panel may not comprise a reflective plate.

The reflectance may be a viewing side reflectance. The viewing sidereflectance may be a reflectance measured in a direction in which anobserver observes the display panel in a state where the panel is used.

In the present application, the term upper substrate means, in a liquidcrystal panel structure comprising liquid crystals interposed betweentwo substrates, a substrate closer to an observer observing an imagedisplayed by the liquid crystal panel among the two substrates.

For example, such an upper substrate may mean a substrate opposite to abacklight side substrate in a transmissive liquid crystal panel,specifically, a substrate farther from the backlight than the lowersubstrate among the upper and lower substrates, which are twosubstrates, and the lower substrate may mean a substrate closer to thebacklight than the upper substrate.

A general liquid crystal panel comprises liquid crystals interposedbetween an upper substrate and a lower substrate. Here, a TFT (thin filmtransistor) capable of applying an electrical signal is present on thelower substrate, a color filter is present on the upper substrate, andthe color filter comprises a so-called BM (black matrix). In generalliquid crystal panels, since the color filter comprising the BM forblocking or absorbing light is present on the upper substrate as above,the reflectance usually shows about 10% (based on a wavelength of 550nm).

The highly reflective liquid crystal panel has, for example, a structurethat comprises no BM, a structure in which the color filter and the BMdo not exist in the upper substrate but exist in the lower substrate ora structure in which the color filter comprising no BM is present on thelower substrate, and the like. In one example, the highly reflectiveliquid crystal panel may be a panel in which a color filter and a TFTare disposed together on a lower substrate, and in such a case, thecolor filter may or may not comprise the BM. The elevated reflectance ofthe highly reflective liquid crystal panel may affect a color sense,especially a color sense of the black state, of the display device. Theterm black state herein is a state in which the liquid crystal panel isadjusted so as to block light from a light source, which may mean, forexample, a state of off-voltage in a normally black mode or a state ofon-voltage in a normally white mode. Furthermore, in the case of a panelcomprising no BM among the highly reflective liquid crystal panels, alarger light leakage due to an increase in an aperture ratio or the likein the black state may be caused, and such a light leakage may bring thecolor sense in the black state close to approximately red or yellow. Thepolarizer or polarizing plate of the present application has opticalcharacteristics to be described below, and such optical characteristicscan maximize the advantages while solving the problems that may occur inthe highly reflective liquid crystal panel as above.

Accordingly, the highly reflective liquid crystal panel to which thepolarizer of the present application is applied may be a liquid crystalpanel comprising no BM, or a liquid crystal panel that a color filterdoes not exist on the upper substrate and exists together with a TFT onthe lower substrate. The liquid crystal panel comprising no BM may ormay not comprise a color filter, and in the case of comprising the colorfilter, this color filter may exist on the lower substrate instead ofthe upper substrate. In addition, in the structure in which the colorfilter and the TFT are simultaneously present on the lower substrate,the color filter may or may not comprise a BM. A liquid crystal panelhaving such a structure, for example, a liquid crystal panel in which acolor filter exists on a lower substrate may be advantageous inrealizing various structures such as a curved surface structure, and maybe advantageous in terms of luminance when no BM is present.

Such a polarizer may be an upper polarizer of the liquid crystal panel.In the present application, the term upper may mean a direction facingan observer who observes images from a display device when the displaydevice implements the images and the term lower may mean the oppositedirection. The upper polarizer may also be referred to as a viewing sidepolarizer in another term. Furthermore, in the present application, theterm lower polarizer may also be referred to as a back side polarizer ora light source side polarizer.

The polarizing plate of the present application may be one whichsatisfies Equation 1 below or satisfies Equation 2 below.0.9≤K1=R1(450)/R1(650)+0.044×exp(0.43×bs)≤1.1  [Equation 1]

In Equation 1, bs means a single color (bs) of the polarizing plate. Inthe present application, the term single color (bs) means a b value inCIE Lab color space (b value in condition 2 to be described below).

In Equation 1, R1 (450) is a reflectance (unit:%) of the polarizingplate for light having a wavelength of 450 nm measured under a statewhere the polarizing plate is positioned on a reflective surface havinga reflectance of about 23% for light having a wavelength of 550 nm, andR1 (650) is a reflectance (unit:%) of the polarizing plate for lighthaving a wavelength of 650 nm measured under a state where thepolarizing plate is positioned on a reflective surface having areflectance of about 23% for light having a wavelength of 550 nm.

In Equation 1, exp is an abbreviation of exponential function.0.9≤K2=R2(450)/R2(650)+0.0026×exp(1.09×bs)≤1.1  [Equation 2]

In Equation 2, bs means a single color (bs) as in Equation 1 of thepolarizing plate.

In Equation 2, R2 (450) is a reflectance (unit:%) of the polarizingplate for light having a wavelength of 450 nm measured under a statewhere the polarizing plate is positioned on a reflective surface havinga reflectance of about 15% for light having a wavelength of 550 nm, andR2 (650) is a reflectance (unit: %) of the polarizing plate for lighthaving a wavelength of 650 nm measured under a state where thepolarizing plate is positioned on a reflective surface having areflectance of about 15% for light having a wavelength of 550 nm.

In Equation 2, exp is an abbreviation of exponential function.

In Equations 1 and 2, R1 (450)/R1 (650) or R2 (450)/R2 (650) is a ratioof a reflectance at a wavelength of 450 nm representing a shortwavelength in the visible light region and a reflectance at a wavelengthof 650 nm also representing a long wavelength in the visible lightregion, which can be defined as neutrality of wavelength dispersion forreflection. The inventors have confirmed that a polarizing plate inwhich the neutrality of wavelength dispersion for reflection and singlecolor satisfy any one of Equations 1 and 2 above can solve the problemof color sense distortion caused by reflected light generated in ahighly reflective panel, and can solve the visibility degradation byreflected light.

The inventors have proposed a polarizing plate useful in a highlyreflective liquid crystal panel having a reflectance for light having awavelength of 550 nm in a level of about 18% to 19% as a highlyreflective liquid crystal panel, in Korean Patent Application No.10-2016-0012170 and Korean Patent Application No. 10-2016-0012172.However, as a result of further studies, it has been confirmed that thepolarizing plate proposed in the above patents has insignificantperformance in, as a liquid crystal panel having a reflectance higherthan that of a general liquid crystal panel, but a reflectance lowerthan the level of about 18% to 19% which is a reflectance proposed inthe above patents, for example, a liquid crystal panel having areflectance for light having a wavelength of 550 nm of less than about18%, about 17% or less, about 16% or less, about 15% or less, about 14%or less, about 13% or less, or about 12.5% or less, or as a liquidcrystal panel having a reflectance higher that the reflectance proposedin the above patents, for example, a liquid crystal panel having areflectance for light having a wavelength of 550 nm of about 20% ormore, about 21% or more, or about 22% or more. However, the polarizingplate proposed in the present application can exhibit an excellenteffect even in the highly reflective panel as above. The upper or lowerlimit of the reflectance of each panel is as described above.

Specific methods of measuring the single color (bs), R (450) and R (650)applied to Equation 1 or 2 are described in the following examples.

In another example, K1 in Equation 1 may be 0.95 or more, or 0.97 ormore. In another example, the K1 may be 1.05 or less, or 1.03 or less.In a suitable example, K1 may have a value close to 1, or be 1.

In another example, K2 in Equation 1 may be 0.95 or more, or 0.97 ormore. In another example, the K2 may be 1.05 or less, or 1.03 or less.In a suitable example, K2 may have a value close to 1, or be 1.

The polarizing plate having the relationship as above can block orabsorb light having a long wavelength, for example, red to yellow serieslight, among the light from the highly reflective panel, for example,the highly reflective liquid crystal panel, thereby improving visualsense characteristic in the black state and solving the problem ofvisibility degradation due to reflected light or the like.

In one example, the polarizing plate satisfying Equation 1 or 2 abovemay have a single transmittance (Ts), that is, a transmittance (Ts) forun-polarized light in a range of about 40% to about 45%. In anotherexample, the transmittance (Ts) may be about 44% or less, about 43% orless, about 42% or less, or about 41% or less. When the singletransmittance (Ts) of the polarizing plate satisfying Equation 1 or 2 isin the above range, the physical properties required in the highlyreflective panel can be effectively satisfied.

In one example, the polarizing plate satisfying Equation 1 or 2 abovemay exhibit a certain range of coordinates in the Lab color space of CIE(international commission on illumination).

The CIE Lab color space is a color space in which the CIE XYZ colorspace is nonlinearly transformed based on human visual antagonistictheory. In this color space, the L value represents brightness, where ifthe L value is 0, it represents black, and if the L value is 100, itrepresents white. Also, if the a value is a negative number, the colorbecomes a color slated to green and if it is a positive number, thecolor becomes a color slanted to red or violet. Furthermore, if the bvalue is a negative number, the color becomes a color slanted to blueand if the b value is a positive number, the color becomes a colorslanted to yellow.

In one example, the polarizing plate may have characteristics obtainedin the CIE Lab color space satisfying any one of the followingconditions 1 to 4.

Condition 1: a −a value of 2 or less in CIE Lab color space:

Condition 2: a b value of 4 or less in CIE Lab color space:

Condition 3: a ratio (−b/a) of −a value and b value of 2.5 or less inCIE Lab color space:

Condition 4: a −bc value of 0.05 to 40 in CIE Lab color space.

In Condition 1, the −a value of the polarizing plate may be, forexample, about 2 or less, less than 2, 1.8 or less, less than 1.8, 1.6or less, or less than 1.6. The −a value may be about 0.7 or more, about0.9 or more, about 1.1 or more, about 1.3 or more, or about 1.4 or more.

In Condition 2, the b value of the polarizing plate is a single color(bs) in Equations 1 and 2 above, which may be about 4 or less, about 3.5or less, less than about 3.5, about 3 or less, less than about 3, about2.5 or less, or less than 2.5 or so. The b value may be about 1.5 ormore, more than about 1.5, about 2 or more, or more than about 2.5.

In Condition 3, the ratio of the −a value and the b value (−b/a,hereinafter may be referred to as C index) may be about 2.5 or less, orless than about 2.5. The C index may be about 1 or more, more than about1, about 1.25 or more, more than about 1.25, about 1.5 or more, or morethan about 1.5.

As Condition 4, the polarizer or polarizing plate may have a −bc valueof 40 or less in the CIE Lab color space. In another example, the −bcvalue may be 38 or less, 36 or less, 34 or less, 32 or less, 30 or less,28 or less, 26 or less, 24 or less, 22 or less, 20 or less, 18 or less,16 or less, 14 or less, 12 or less, 10 or less, 8 or less, 6 or less, 4or less, 2 or less, 1 or less, or 0.5 or less. In another example, the−bc value may be 0.01 or more, 0.05 or more, 0.1 or more, 0.5 or more, 1or more, 2 or more, 4 or more, 6 or more, 8 or more, 10 or more, 12 ormore, 14 or more, 16 or more, 18 or more, 20 or more, 22 or more, 24 ormore, or 26 or more. The −bc value may be in the range by any onecombination of any one of the upper limits and any one of the lowerlimits as described above. The polarizer has a light absorption axisformed in one direction. Here, the −bc value may be a value in which theb value in the CIE Lab color space, as measured using linearly polarizedlight polarized parallel to the light absorption axis, is multiplied by−1. That is, the a value and the b value in Conditions 1 to 3 may be thea value and the b value measured for un-polarized light. The bc valuemay be measured, for example, in the same manner as when measuring the bvalue, in a state where light absorption axes of two polarizers orpolarizing plates are arranged to be vertical to each other.

The polarizer or polarizing plate may satisfy any one or two or more ofConditions 1 to 4 above, or all the above conditions. Such a polarizeror a polarizing plate can be applied to a liquid crystal panel, inparticular, the above-mentioned highly reflective liquid crystal panel,to improve the disadvantages, for example, the visual sense in the blackstate while maintaining or maximizing the advantages of the liquidcrystal panel. Although the reason is unclear, the polarizer having theoptical characteristics as above can block or absorb light of a longwavelength, for example, red to yellow series light, in the light fromthe liquid crystal panel, thereby improving the visual sensecharacteristics in the black state.

In one example, the polarizer or polarizing plate may satisfy at leastCondition 2 in Conditions 1 to 4 above and further satisfy Conditions 1and/or 3. In another example, the polarizer or polarizing plate maysatisfy at least Condition 3 above and further satisfy Conditions 1and/or 2. Furthermore, in another example, the polarizer or polarizingplate may satisfy all Conditions 1 to 3 above. Also, in another example,the polarizer or polarizing plate may satisfy at least Condition 4 aboveand further satisfy at least one of Conditions 1 to 3.

For example, the polarizer or polarizing plate may satisfy at leastConditions 2 and 4 and further satisfy Conditions 1 and/or 3, or maysatisfy at least Conditions 3 and 4 and further satisfy Conditions 1and/or 2, or may satisfy all Conditions 1 to 4 above.

Each numerical value in the CIE Lab color space can be measured byapplying a general method of measuring each coordinate of the colorspace, and for example, can be measured according to a manufacturer'smanual after positioning an equipment with an integrating sphere typedetector (spectrophotometer) (ex. CM-2600d, KONICA MINOLTA) at ameasuring position. In one example, each coordinate of the CIE Lab colorspace may also be measured under a state where the polarizer orpolarizing plate is attached to a liquid crystal panel, for example, ahighly reflective liquid crystal panel, or may also be measured for thepolarizer or polarizing plate itself.

The polarizing plate can satisfy other functions required for thepolarizing plate while exhibiting the above-described opticalcharacteristics.

For example, the polarizing plate may have a minimum transmittance (Tc)of about 0.01% or less, about 0.009% or less, about 0.006% or less,about 0.005% or less, about 0.004% or less, about 0.001% or less, orabout 0.0009% or less. The minimum transmittance (Tc) may be about0.0001% or more. In the present application, the term minimumtransmittance (Tc) may mean the minimum value of transmittance appearingwhen having measured transmittances while scanning the overlapping statein which a light absorption axis of each polarizer forms angles in therange of 0 to 360 degrees for each angle under a state where twopolarizing plates are overlapped. Here, at least one polarizing plate ofthe two overlapping polarizing plates may be a polarizing plateaccording to the present application, or a different polarizing plate,for example, a polarizing plate provided in the measuring equipment.

The polarizing plate may have a polarization degree of about 99.9% ormore, or about 99.99% or more. The polarization degree in the presentapplication is a numerical value calculated according to Equation Abelow.Polarization degree(P)(%)={(Tp−Tc)/(Tp+Tc)}^(1/2)×100  [Equation A]

In Equation A, Tp is the maximum transmittance of the polarizing plate,and Tc is the minimum transmittance as described above.

In Equation A, the maximum transmittance (Tp) may be a transmittance ata time showing the maximum value when having measured transmittanceswhile scanning the overlapping state such that a light absorption axisof each polarizer forms angles in the range of 0 to 360 degrees for eachangle under a state where two polarizing plates are overlapped. Here, atleast one polarizing plate of the two overlapping polarizing plates maybe a polarizing plate according to the present application, or adifferent polarizing plate, for example, a polarizing plate provided inthe measuring equipment.

The above-mentioned transmittances (Ts, Tc, Tp) are values measured forlight of about 550 nm.

The polarizing plate exhibiting such transmittance and polarizationdegree can be applied to a liquid crystal panel to exhibit excellentlight transmission or blocking function.

The method for producing the polarizing plate as above is notparticularly limited. For example, the polarizing plate, that is, apolarizing plate which may basically satisfy Equation 1 or 2 andoptionally show coordinates in the above-described CIE Lab color space,can be produced by adjusting absorption rates of the polarizer includedin the polarizing plate for each wavelength or by a method of adjustingother components included therein together with the polarizer. Forexample, the polarizer included in the polarizing plate or thepolarizing plate may have a light-blocking rate in a range of about 5.1to 6.0 for light having any one wavelength in a range of about 560 nm toabout 750 nm, for example, light having a wavelength of about 700 nm. Inanother example, the polarizing plate or polarizer may have alight-blocking rate in the range of about 1 to 5 or 1.5 to 4.5 or 1.5 to4, or 1.5 to 3.5 or 1.5 to 3 for light at a wavelength of 550 nm. Here,the light having any one wavelength in a range of about 560 nm to about750 nm may be the linearly polarized light polarized at any one anglewithin a range of approximately −5 to 5 degrees, any one angle within arange of approximately −3 to 3 degrees with, or approximately parallelto a light absorption axis of the polarizer. Also, the light-blockingrate herein may mean, for example, absorbance.

The absorbance is calculated by an equation −log (Tc), where Tc may bethe minimum transmittance as described above.

The method of performing so that the polarizer exhibits theabove-described light-blocking rate is not particularly limited. Thepolarizing plate may comprise, for example, a PVA-based polarizer whichis a typical absorptive polarizer. The PVA-based polarizer generallycomprises a PVA film and an anisotropic absorbent material such as adichroic pigment or iodine adsorbed and oriented on the PVA film, wherethe light-blocking rate can be adjusted through adjustment of the ratioor kind of the anisotropic absorbent material.

For example, the PVA-based polarizer may be produced by subjecting aPVA-based film to various treatments such as swelling, dyeing,cross-linking and stretching, followed by cleaning and drying processes,where the light-blocking rate may be controlled by adjusting processconditions in any one process of the above processes, or throughadditional processes. For example, the dyeing process can be performedby immersing the PVA-based film in a treatment tank containing iodineand potassium iodide, where the light-blocking rate can be adjustedthrough a process of adjusting concentrations of iodine and/or potassiumiodide in the treatment tank, or further removing or supplementing atleast one ingredient of the iodine and/or potassium iodide adsorbedafter dyeing in this process. The method of adjusting the light-blockingrate is one example in which the polarizing plate of the presentapplication can be produced.

It is also possible to prepare a polarizing plate or polarizer havingthe above-mentioned characteristics and/or light-blocking rate byadjusting concentrations of I₂, iodide and a boric acid compound (boricacid or borate) in the dyeing and cross-linking processes performed inthe production process of the polarizer. That is, the polarizer isusually produced by dyeing and cross-linking a PVA (poly(vinyl alcohol))film, where a swelling process is also performed before the dyeingprocess. In the above process, in order to dye a PVA film with iodine, aprocess of dyeing and cross-linking the PVA film with a dyeing solutionor a cross-linking solution containing iodide such as iodine (I₂) and KIand/or a boric acid compound (boric acid or borate) is performed, wherein the above process the concentration of the compound in the aqueoussolution influences the color sense of the polarizer or polarizingplate.

For example, compound species of the iodine compounds that may bepresent in the dyeing solution and the cross-linking solution mayinclude I⁻, I₂, I₃ ⁻, I₅ ⁻ derived from iodide (M⁺I⁻) and iodine (I₂),and the like. However, among these compounds, I⁻ has an absorptionwavelength range of about 190 nm to 260 nm, the effect on the colorsense of which is insignificant, I₂ has an absorption wavelength rangeof about 400 nm to 500 nm, the color sense of which is mainly red, I₃ ⁻has an absorption wavelength range of about 250 nm to 400 nm, the colorsense of which is mainly yellow, and I₅ ⁻ has an absorption wavelengthrange of about 500 nm to 900 nm, the color sense of which is mainlyblue.

As described above, I₂, I₃ ⁻ and I₅ ⁻ mainly affect the color sense.However, among the iodine species, I₃ ⁻ is generated in proportion tothe concentration of iodide when iodide has been added in a relativelyexcess amount over iodine. In addition, the ratio of I₅ ⁻ is inproportion to the concentration of the boric acid compound (boric acidor borate). Therefore, I₃ ⁻ can be controlled by the concentration ofiodide and I₅ ⁻ can be controlled by the concentration of the boric acidcompound.

As described above, a method of controlling concentrations of chemicalspecies in a dyeing solution or a cross-linking solution is known.

Therefore, it is possible to produce a polarizing plate or polarizerhaving the above-mentioned characteristics and/or light-blocking rate byadjusting the concentrations of the chemical species in the dyeingsolution or the cross-linking solution in a known manner inconsideration of the absorption wavelength range and color sense of eachchemical species.

For example, the polarizer or polarizing plate of orange or yellowseries is produced by applying a dyeing solution or a cross-linkingsolution having relatively high concentrations of I₂ and/or I₃ ⁻, andthe polarizer or polarizing plate of blue series is produced by applyinga relatively high concentration of the boric acid compound.

Also, the light-blocking rate can be adjusted in consideration of theabsorption wavelength range of each chemical species, and theabove-described characteristics, for example, the be value, and the likecan also be adjusted by controlling a draw ratio, that is, orientationof iodine to be adsorbed.

The aforementioned dyeing solution and/or cross-linking solution in thedyeing and/or cross-linking processes is prepared by dissolving iodine(I₂) and iodide (KI etc.) or iodine (I₂), iodide (KI etc.) and a boricacid compound in a solvent (ex. water). In one example, a polarizingplate satisfying the requirements set forth in the present applicationmay be produced by using a dyeing solution or cross-linking solution inwhich a weight ratio of the iodine and iodide (iodide/iodine) iscontrolled in the range of about 1 to 100 in consideration of theconcentration of each chemical species, or by using a dyeing solution orcross-linking solution in which a weight ratio of the iodine and iodide(iodide/iodine) is in the range of about 1 to 100 and the concentrationof the boric acid compound is controlled in the range of approximately0.1 to 10 wt %. If necessary, a polarizing plate or polarizer satisfyingthe above conditions may be produced by adjusting the draw ratiotogether in the range to be described below.

As described above, the production of the polarizing plate or polarizersatisfying the requirements set forth in the present application is easyin a polarizing plate comprising a PVA series polarizer. Accordingly,the polarizing plate of the present application may comprise a polarizercomprising a PVA-based film and an anisotropic absorbent materialadsorbed and oriented on the PVA-based film. Here, the anisotropicabsorbent material may be iodine. That is, the polarizer may be aniodine- and PVA-based polarizer.

As the PVA-based film, for example, the conventionally used PVA-basedfilm may be used. A material of such a PVA-based film may include PVA ora derivative thereof. The derivative of PVA may include polyvinylformalor polyvinyl acetal, and the like, and may also include those modifiedby olefins such as ethylene or propylene, unsaturated carboxylic acidssuch as acrylic acid, methacrylic acid or crotonic acid and alkyl estersthereof or acrylamide, and the like. The PVA has a polymerization degreeof about 100 to 10000 or about 1000 to 10000, and a saponificationdegree of about 80 to 100 mol %, but is not limited thereto. As thePVA-based film, a hydrophilic polymer film such as a partiallysaponified film of ethylene-vinyl acetate copolymer series or apolyene-based alignment film such as a dehydrated product of PVA or adehydrochlorinated product of polyvinyl chloride, and the like may alsobe exemplified.

The PVA-based film may contain an additive such as a plasticizer or asurfactant. The plasticizer may be exemplified by polyol and acondensate thereof, and for example, may be exemplified by glycerin,diglycerin, triglycerin, ethylene glycol, propylene glycol orpolyethylene glycol, and the like. When such a plasticizer is used, theratio thereof is not particularly limited and may be generally about 20wt % or less in the PVA-based film.

The thickness of the PVA-based film is not particularly limited, and canbe suitably selected within a range in which each of the above-describedoptical characteristics can be satisfied.

The kind of the anisotropic absorbent material that can be included inthe polarizer is also not particularly limited. In the presentapplication, among the known anisotropic absorbent materials, thosecapable of satisfying the above-described optical characteristics can beappropriately selected. An example of the anisotropic absorbent materialcan be exemplified by iodine. The ratio of the anisotropic absorbentmaterial in the polarizing plate is also not particularly limited aslong as it can satisfy the above-described optical characteristics, andthose skilled in the art can easily set the range through simpleexperiment or prediction.

Such a polarizer can be produced, for example, by performing at least adyeing process, a cross-linking process and a stretching process on thePVA-based film. In the dyeing process, the cross-linking process and thestretching process, the respective treatment tanks of a dyeing bath, across-linking bath and a stretching bath are used, respectively, and inthese respective treatment tanks, a treatment solution according to eachprocess can be used.

In the dyeing process, an anisotropic absorbent material such as iodinecan be adsorbed and/or oriented on the PVA-based film. Such a dyeingprocess can be performed together with the stretching process. Thedyeing can generally be carried out by immersing the film in a solutioncontaining an anisotropic absorbent material, for example, an iodinesolution. As the iodine solution, for example, an aqueous solution inwhich iodine ions are contained by iodine and an iodinated compound as asolubilizing agent may be used. As the iodinated compound, for example,potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminumiodide, lead iodide, copper iodide, barium iodide, calcium iodide, tiniodide or titanium iodide, and the like can be used. The concentrationsof iodine and/or iodide ions in the iodine solution can be adjusted soas to achieve a light-blocking rate capable of satisfying theabove-described optical characteristics. However, process parameters canbe adjusted so that the light-blocking rate can be achieved even by anadditional process other than the dyeing step, and in such a case, theconcentration in the dyeing process may be applied in a usual range. Inthe dyeing step, the temperature of the iodine solution is usually 20 to50° C. or 25 to 40° C. or so, and the immersion time is usually 10 to300 seconds or 20 to 240 seconds or so, without being limited thereto.The light-blocking rate can also be controlled by adjusting theconcentration of the iodine solution and/or the immersion time thereof.

The cross-linking process carried out in the production process of thepolarizer can be carried out, for example, using a cross-linking agentsuch as a boron compound. The order of such a cross-linking process isnot particularly limited, and the process can be performed, for example,with the dyeing and/or stretching processes, or can proceed separately.The cross-linking process may also be carried out several times. As theboron compound, boric acid or borax may be used. The boron compound canbe generally used in the form of an aqueous solution or a mixed solutionof water and an organic solvent, and usually an aqueous solution ofboric acid is used. The boric acid concentration in the boric acidaqueous solution can be selected in an appropriate range inconsideration of the cross-linking degree and the heat resistancethereof. An iodinated compound such as potassium iodide can be containedin an aqueous solution of boric acid or the like, and theabove-described light-blocking rate can also be controlled throughcontrol of the concentration of such a compound.

The cross-linking process can be carried out by immersing the PVA-basedfilm in an aqueous solution of boric acid, or the like, and in thisprocess, the treatment temperature is usually in a range of 25° C. orhigher, 30° C. to 85° C. or 30° C. to 60° C., and the treatment time isusually 5 seconds to 800 seconds or 8 seconds to 500 seconds or so,without being limited thereto.

The stretching process is generally performed by uniaxial stretching.Such stretching may also be performed together with the dyeing and/orcross-linking processes. The stretching method is not particularlylimited, and for example, a wet stretching method can be applied. Insuch a wet stretching method, for example, stretching after dyeing isgenerally carried out, but stretching may be carried out together withcross-linking, and may be carried out several times or in multiplestages.

The iodinated compound such as potassium iodide can be contained in thetreatment liquid applied to the wet stretching method and thelight-blocking rate can also be controlled through control of the ratioin this process. In the stretching, the treatment temperature is usuallyin the range of 25° C. or higher, 30° C. to 85° C., or 50° C. to 70° C.or so, and the treatment time is usually 10 seconds to 800 seconds or 30seconds to 500 seconds, without being limited thereto.

The total draw ratio in the stretching processes can be controlled inconsideration of the orientation characteristics and the like, and thetotal draw ratio may be about 3 to 10 times, 4 to 8 times, or 5 to 7times or so based on the original length of the PVA-based film, but isnot limited thereto. Here, in the case of involving the stretching evenin the swelling process or the like other than the stretching process,the total draw ratio may mean the cumulative draw ratio including thestretching in each process. Such a total draw ratio can be adjusted inconsideration of orientation, workability or stretching cut possibility,and the like.

In addition to the dyeing, cross-linking and stretching, the swellingprocess may also be performed before the processes are performed. It ispossible to clean contamination of the PVA-based film surface, or anantiblocking agent by swelling, and there is also an effect capable ofreducing unevenness such as dyeing deviation by the swelling.

In the swelling process, water, distilled water or pure water, and thelike can be usually used. The main component of the relevant treatmentliquid is water, and if necessary, a small amount of an iodinatedcompound such as potassium iodide or an additive such as a surfactant,or alcohol, and the like can be included therein. In this process, it isalso possible to adjust the light-blocking rate by controlling processvariables.

The treatment temperature in the swelling process is usually 20° C. to45° C. or so, or 20° C. to 40° C. or so, but is not limited thereto.Since the swelling deviations can cause dyeing deviations, the processvariables can be adjusted so that the occurrence of such swellingdeviations is suppressed as much as possible.

The proper stretching may also be performed in the swelling process. Thedraw ratio may be 6.5 times or less, 1.2 to 6.5 times, 2 times to 4times, or 2 times to 3 times, based on the original length of thePVA-based film. The stretching in the swelling process can control thestretching in the stretching process performed after the swellingprocess to be small and can control so that the stretching failure ofthe film does not occur.

In the production process of the polarizer, a metal ion treatment can beperformed. Such a treatment is carried out, for example, by immersingthe PVA-based film in an aqueous solution containing a metal salt. Thisallows metal ions to be contained in the polarizer, and in this process,the color tone of the PVA-based polarizer can also be adjusted bycontrolling the kind or ratio of the metal ions. As the metal ion thatcan be applied, metal ions of transition metals such as cobalt, nickel,zinc, chromium, aluminum, copper, manganese or iron can be exemplified,and the color tone can also be adjusted by selecting a proper kind amongthem.

After the dyeing, cross-linking and stretching, a cleaning process mayproceed. Such a cleaning process can be performed by a solution of aniodinated compound such as potassium iodide, and in this process, theabove-described light-blocking rate can also be adjusted through theconcentration of the iodinated compound in the solution or the treatmenttime of the cleaning process, and the like. Therefore, the concentrationof the iodinated compound and the time of treatment into the solutioncan be adjusted in consideration of the light-blocking rate. However,the cleaning process may also be performed using water.

This cleaning with water may also be combined with cleaning with thesolution of an iodinated compound, where a solution in which liquidalcohols such as methanol, ethanol, isopropyl alcohol, butanol orpropanol are blended may also be used.

After passing through such a process, the polarizer can be produced byperforming a drying process. In the drying process, for example, it maybe carried out at an appropriate temperature for a suitable time inconsideration of the required moisture content and the like, and suchconditions are not particularly limited.

When the polarizing plate of the present application comprises aPVA-based polarizer, the desired polarizing plate can be obtainedthrough control of the process variables in the respective processes.However, although the contents have been mainly explained through thepolarizing plate comprising the PVA-based polarizer, the applicablepolarizing plate is not limited to the polarizing plate, and other knownpolarizing plates can satisfy the above-described characteristics byadjusting the light-blocking rate and the like by a known method.

Other components that can be included in the polarizing plate of thepresent application can be exemplified by a protective film of apolarizing plate, a pressure-sensitive adhesive layer, an adhesivelayer, a retardation film or a low-reflection layer, and the like. Ifnecessary, the overall characteristics of the polarizing plate can beadjusted through control the other components, thereby improvingsuitability for applications in the present application. For example,the required level of physical properties can be adjusted so that theycan be achieved by adjusting the overall light-blocking rate of thepolarizing plate in such a manner that a specific pigment or dye iscontained in the protective film, the pressure-sensitive adhesive layer,the adhesive layer, the retardation film and/or the low-reflectionlayer.

As the protective film that can be included in the polarizing plate, afilm of a known material can be used. As such a material, for example, athermoplastic resin having excellent transparency, mechanical strength,thermal stability, moisture barrier property or isotropy, and the likecan be used. An example of such a resin can be exemplified by acellulose resin such as triacetyl cellulose (TAC), a polyester resin, apolyethersulfone resin, a polysulfone resin, a polycarbonate resin, apolyamide resin, a polyimide resin, a polyolefin resin, a (meth)acrylicresin, a cyclic polyolefin resin such as a norbornene resin, apolyarylate resin, a polystyrene resin, a polyvinyl alcohol resin or amixture thereof, and the like. For example, the protective film may bepresent on one side or both sides of a polarizing plate, and whenpresent on both sides, each protective film may be the same ordifferent. In addition to the protective film in film form, a curedresin layer obtained by curing a thermosetting or photo-curing resinsuch as (meth)acryl series, urethane series, acrylic urethane series,epoxy series or silicone series may also be applied as the protectivefilm.

The thickness of the protective film can be appropriately adjusted,which can be usually adjusted within the range of 1 to 500 μm, 1 to 300μm, 5 to 200 μm, or 5 to 150 μm from the viewpoints of workability suchas strength or handleability, or thinning, and the like.

As the retardation film, a general material can be applied, and forexample, a uniaxially or biaxially stretched birefringent polymer filmor an alignment film of a liquid crystal polymer, and the like can beapplied. Also, the thickness of the retardation film is not particularlylimited.

The protective film or retardation film as described above may beattached to a polarizer or the like by an adhesive or the like, where anadhesion facilitating treatment such as corona treatment, plasmatreatment, primer treatment or saponification treatment can be performedon such a protective film.

Furthermore, when a protective film is attached to a polarizer or thelike, a hard coat layer, a low-reflection layer, an antireflectionlayer, a sticking prevention layer, a diffusion layer or a haze layer,and the like may be present on the side opposite to the side where theprotective film is attached to the polarizer. The physical properties ofthe polarizer can also be adjusted through control of characteristics ofsuch a layer.

In addition to the protective film or the retardation film, for example,various components such as a reflective plate or a semi-transmissiveplate may also be present in the polarizing plate, and the kind thereofis not particularly limited.

An adhesive may be used for adhesion of a protective film or the like.The adhesive may be exemplified by an isocyanate adhesive, a polyvinylalcohol adhesive, a gelatin adhesive, a vinyl-, latex- or water-basedpolyester, and the like can be exemplified, but is not limited thereto.As the adhesive, a water-based adhesive may be used, but depending onthe type of the film to be attached, a solvent-free type photo-curableadhesive may also be used.

For attaching to other members such as a liquid crystal panel, apressure-sensitive adhesive layer can be included in the polarizingplate. The pressure-sensitive adhesive for forming thepressure-sensitive adhesive layer is not particularly limited, and forexample, an acrylic polymer, a silicone polymer, polyester,polyurethane, polyamide, polyether or a polymer such as a fluorine-basedor rubber-based polymer can be appropriately selected and used. Theadhesion of the pressure-sensitive adhesive layer to one side or bothsides of the polarizing plate can be carried out in an appropriatemanner, and the manner thereof is not particularly limited.

With respect to the exposed surface of the pressure-sensitive adhesivelayer, a release film may be temporarily attached thereto and coveredfor the purpose of preventing the contamination until the layer isprovided for practical use.

The polarizer, protective film or pressure-sensitive adhesive layer, andthe like included in the polarizing plate may be provided with anultraviolet absorbing ability. Such an ultraviolet absorbing ability canbe realized by, for example, comprising an ultraviolet absorber in anappropriate proportion in each component. As the ultraviolet absorber, asalicylic ester-based compound, a benzophenol-based compound, abenzotriazole-based compound, a cyanoacrylate-based compound or a nickelcomplex salt-based compound, and the like may be used, without beinglimited thereto.

The present application also relates to a display device. The displaydevice may comprise at least the polarizing plate. In one example, thedisplay device may comprise a liquid crystal panel and the polarizingplate disposed on one side of the liquid crystal panel. At this time,the polarizing plate may be included as an upper polarizing plate, thatis, a viewing side polarizing plate. Here, the liquid crystal panel maycomprise an upper substrate and a lower substrate, and may comprise aliquid crystal layer between the upper substrate and the lowersubstrate. At this time, the liquid crystal panel may be a highlyreflective liquid crystal panel, for example, a liquid crystal panelcomprising no BM. Also, the liquid crystal panel may be a liquid crystalpanel in which a TFT and a color filter are both present on the lowersubstrate side. In such a structure, the polarizing plate can improvethe disadvantages, for example, the reflective visual sensecharacteristics in the black state while maintaining or maximizing theadvantages of the liquid crystal panel. As described above, the liquidcrystal panel is a transmissive liquid crystal panel, for example, aliquid crystal panel comprising no reflective plate.

In one example, the display device may comprise an additional polarizingplate (hereinafter, referred to as a second polarizing plate). Forexample, the above-described polarizing plate (hereinafter, referred toas a first polarizing plate) of the present invention may be disposed onthe upper side of the liquid crystal panel, that is, the viewing side,and the second polarizing plate may be disposed on the lower side, thatis, the back side or the light source side. In this case, the secondpolarizing plate may be, for example, one adjusted so that thelight-blocking rate (light absorption rate or light reflectance) at anyone wavelength within a range of 380 nm to 520 nm is 4 to 6 or so. Here,the light-blocking rate may be, for example, the same concept as theabsorbance described above. The method of controlling the light-blockingrate of the second polarizer plate as above is not particularly limited,and a known method may be applied. In the case of applying the firstpolarizing plate of the present application as the upper polarizingplate of the above-described highly reflective liquid crystal panel, ifthe optical characteristics of the second polarizing plate are adjustedas above, the display characteristics in the black state and the whitestate can be greatly improved.

The specific structure of the highly reflective liquid crystal panel isnot particularly limited. For example, the liquid crystal panel may havethe same structure as that of a known liquid crystal panel except forcomprising no BM. In this case, the color filter may also be present onany substrate side of the upper and lower substrates, and suitably, maybe present on the lower substrate side. Also, the type of the liquidcrystal layer included in the liquid crystal panel is not particularlylimited, and for example, all known mode liquid crystal layers such asVA, IPS, TN or STN can be applied.

Advantageous Effects

In the present application, a polarizing plate can be provided, whichcan be applied to a display device comprising a highly reflective panelto solve disadvantages while maintaining advantages of the device. Inthe present application, a display device comprising the polarizingplate and the highly reflective panel can also be provided.

MODE FOR INVENTION

Hereinafter, the polarizing plate and the like will be described in moredetail through examples and the like according to the presentapplication, but the scope of the present application is not limited tothe following.

Hereinafter, each physical property was measured in the followingmanner.

1. Measurement of Transmittance, Polarization Degree and ColorCoordinate in CIE Lab

In the following examples, the transmittance, polarization degree or CIEcolor coordinate, and the like were measured for the polarizing plateitself according to the manufacturer's manual using a JASCO V-7100spectrophotometer. Furthermore, the transmittance and polarizationdegree were measured for light having a wavelength of 550 nm, and inTables below, as and bs are values of a and b in the CIE Lab color spaceas measured for one polarizing plate, and ac and be are values of a andb in the CIE Lab color space as measured in a state where two polarizingplates are overlapped so that their light absorption axes areperpendicular to each other.

2. Measurement of R1 (450), R2 (450), R1 (650) and R2 (650)

An equipment with an integrator type detector (spectrophotometer)(CM-2600d, KONICA MINOLTA) was positioned at a measuring position in astate where a polarizing plate was attached to a liquid crystal panelhaving a reflectance of about 23% for light having a wavelength of 550nm (in the case of R1 (450) and R1 (650)) or a liquid crystal panelhaving a reflectance of about 15% for light having a wavelength of 550nm (in the case of R2 (450) and R2 (650)), and R1 (450), R2 (450), R1(650) and R2 (650) were measured according to the manufacturer's manual.

Production of Polarizer Sample

The polarizer sample was produced by performing the following swelling,dyeing, cross-linking, stretching and cleaning processes on a PVA filmhaving an average polymerization degree of about 2,400 and a thicknessof about 60 μm as a discotic film. The process variables in the aboveprocesses, for example, the concentration of iodine or iodine ions inthe treatment liquid and the treatment time into the treatment liquid,were adjusted so that the characteristics as shown in Tables 1 to 4below were implemented for each sample. The swelling was carried out byimmersing the PVA film in a swelling bath for an appropriate time usingpure water as the treatment liquid. In addition, the dyeing process wascarried out by immersing the PVA film in a dyeing solution, in which theconcentrations of iodine and potassium iodide were adjusted, at anappropriate temperature for a suitable time and in this process, the PVAfilm was stretched to an appropriate range. The cross-linking processwas carried out by immersing the PVA film in an aqueous solutioncontaining boric acid and potassium iodide in an appropriate ratio asthe treatment liquid in the cross-linking bath and stretching the filmto a predetermined range, and the stretching process was also carriedout in a treatment liquid containing boric acid and potassium iodide ina predetermined concentration as the treatment liquid in the stretchingbath. Subsequently, the cleaning process using an aqueous solutioncontaining potassium iodide in a predetermined ratio as the treatmentliquid in the cleansing bath and the drying process were passed throughto produce a sample. The characteristics of each sample are as follows.In the above processes, the physical properties (numerical values in CIELab color coordinates or the like) of the polarizing plate can becontrolled by adjusting the concentration of iodine or iodine ions inthe treatment liquid and the draw ratio, and the like.

TABLE 1 R1 R1 (450) (650) Ts Tc P bs (%) (%) K1 (%) (%) (%) Sample 10.55 8.56 9.13 0.99 41.95 0.0085 99.9751 Sample 2 1.95 8.23 9.32 0.9842.41 0.0017 99.9832 Sample 3 2.45 8.13 9.15 1.01 42.35 0.002 99.9903Sample 4 2.49 8.16 9.2 0.91 42.33 0.0027 99.991 K1: value calculated byEquation 1 (rounded to two decimal places) Ts: single transmittance(based on a wavelength of 550 nm) Tc: minimum transmittance (based on awavelength of 550 nm) P: polarization degree (based on a wavelength of550 nm)

TABLE 2 CIE-single CIE-crossed −a b C index a b Sample 1 0.57 0.55 0.9615.1 −27.6 Sample 2 1.31 1.95 1.61 4.78 −10.7 Sample 3 1.56 2.45 1.442.78 −6.22 Sample 4 1.53 2.49 1.63 2.5 −5.5 CIE-single: color spacecoordinate measured for one polarizing plate CIE-crossed: color spacecoordinate measured in a state where light absorption axes of twopolarizing plates are crossed at 90 degrees to each other

TABLE 3 R2 R2 (450) (650) Ts Tc P bs (%) (%) K2 (%) (%) (%) Sample 50.53 5.54 5.51 1.01 41.95 0.0085 99.9751 Sample 6 2.26 5.49 5.63 1.0142.09 0.0027 99.9919 Sample 7 2.46 5.48 5.71 1 42.04 0.0017 99.9949Sample 8 3.44 5.11 5.75 1 42.08 0.0017 99.9979 K2: value calculated byEquation 2 (rounded to two decimal places) Ts: single transmittance(based on a wavelength of 550 nm) Tc: minimum transmittance (based on awavelength of 550 nm) P: polarization degree (based on a wavelength of550 nm)

TABLE 4 CIE-single CIE-crossed −a b C index a b Sample 5 0.55 0.53 0.9615.22 −27.4 Sample 6 1.52 2.26 1.49 3.31 −6.43 Sample 7 1.57 2.46 1.571.87 −3.91 Sample 8 1.78 3.44 1.93 0.29 −0.64 CIE-single: color spacecoordinate measured for one polarizing plate CIE-crossed: color spacecoordinate measured in a state where light absorption axes of twopolarizing plates are crossed at 90 degrees to each other

Test Example

The polarizing plate of each sample was attached on the upper substrateof the liquid crystal panel, in which both the color filter and the TFTwere present on the lower substrate and thus the reflectance of theupper substrate side for light having a wavelength of 550 nm was about12% or more, as a liquid crystal panel, and the visual sense in theblack state was evaluated visually. As a result of the evaluation, whenthe polarizing plate of each sample was attached, the screen wasrecognized as black in the black state, whereby the visual sense in theblack state was excellent. In addition, as a result of measuring thereflectance for light having a wavelength of about 650 nm on theattached side (upper substrate side) of the polarizing plate in theliquid crystal panel in each state, it can be confirmed that when thepolarizing plates of Examples are attached, the reflectance is 9% orless all, and the reflective visual sense can be also improved.

The invention claimed is:
 1. A polarizing plate applied to a displaypanel having a reflectance of 12% or more for light having a wavelengthof 550 nm, wherein the polarizing plate has a K1 value calculated byEquation 1 below in a range of 0.9 to 1.1:K1=R1(450)/R1(650)+0.044×exp(0.43×bs)  [Equation 1] wherein, bs is asingle color of the polarizing plate, R1 (450) is a reflectance (unit:%)of the polarizing plate for light having a wavelength of 450 nm measuredunder a state where the polarizing plate is positioned on a reflectivesurface having a reflectance of 23% for light having a wavelength of 550nm, and R1 (650) is a reflectance (unit:%) of the polarizing plate forlight having a wavelength of 650 nm measured under a state where thepolarizing plate is positioned on a reflective surface having areflectance of 23% for light having a wavelength of 550 nm, and furthersatisfying at least one condition of the following conditions 1 to 4 andat least two conditions of Conditions 1 to 3: Condition 1: a −a value of2 or less in CIE Lab color space; Condition 2: a b value of 4 or less inCIE Lab color space; Condition 3: a ratio (−b/a) of −a value and b valueof 2.5 or less in CIE Lab color space; Condition 4: a −bc value of 0.05to 40 in CIE Lab color space; and wherein the polarizing plate has apolarizer comprising a PVA-based film and an anisotropic absorbentmaterial adsorbed and oriented on the PVA-based film.
 2. The polarizingplate according to claim 1, wherein the polarizing plate has a singletransmittance (Ts) in a range of 40% to 45%.
 3. The polarizing plateaccording to claim 1, satisfying Condition 2 and further satisfyingCondition 1 or
 3. 4. The polarizing plate according to claim 1,satisfying Condition 3 and further satisfying Condition 1 or
 2. 5. Thepolarizing plate according to claim 1, satisfying all Conditions 1 to 3.6. The polarizing plate according to claim 1, wherein the polarizingplate has a light absorption axis formed in one direction and atransmittance (Tc) of 0.01% or less for linearly polarized light formingan angle in a range of −5 degrees to 5 degrees with the light absorptionaxis.
 7. The polarizing plate according to claim 1, wherein thepolarizing plate has a polarization degree of 99.9% or more.
 8. Thepolarizing plate according to claim 1, wherein the polarizing plate hasa light-blocking rate in a range of 5.1 to 6.0 for light having any onewavelength in a range of 560 nm to 750 nm.
 9. The polarizing plateaccording to claim 1, further comprising a polarizer protective film, apressure-sensitive adhesive layer, an adhesive layer, a retardation filmor a low-reflection layer.
 10. A display device comprising thepolarizing plate of claim
 1. 11. The display device according to claim10, further comprising a liquid crystal panel having a reflectance of12% or more for light having a wavelength of 550 nm, wherein thepolarizing plate is disposed on the viewing side of the liquid crystalpanel.
 12. The display device according to claim 11, further comprisinga second polarizing plate disposed on the back side of the liquidcrystal panel.
 13. The display device according to claim 12, wherein thesecond polarizing plate has a light-blocking rate in a range of 4 to 6at any one wavelength in a range of 380 nm to 520 nm.
 14. A polarizingplate applied to a display panel having a reflectance of 12% or more forlight having a wavelength of 550 nm, wherein the polarizing plate has aK2 value calculated by Equation 2 below in a range of 0.9 to 1.1:K2=R2(450)/R2(650)+0.0026×exp(1.09×bs)  [Equation 2] wherein, bs is asingle color of the polarizing plate, R2 (450) is a reflectance (unit:%)of the polarizing plate for light having a wavelength of 450 nm measuredunder a state where the polarizing plate is positioned on a reflectivesurface having a reflectance of 15% for light having a wavelength of 550nm, and R2 (650) is a reflectance (unit:%) of the polarizing plate forlight having a wavelength of 650 nm measured under a state where thepolarizing plate is positioned on a reflective surface having areflectance of 15% for light having a wavelength of 550 nm, and furthersatisfying at least one condition of the following conditions 1 to 4 andat least two conditions of Conditions 1 to 3: Condition 1: a −a value of2 or less in CIE Lab color space; Condition 2: a b value of 4 or less inCIE Lab color space; Condition 3: a ratio (−b/a) of −a value and b valueof 2.5 or less in CIE Lab color space; Condition 4: a −bc value of 0.05to 40 in CIE Lab color space; and wherein the polarizing plate has apolarizer comprising a PVA-based film and an anisotropic absorbentmaterial adsorbed and oriented on the PVA-based film.
 15. A polarizingplate applied to a viewing side of a liquid crystal panel having areflectance of 12% or more for light having a wavelength of 550 nm,wherein the polarizing plate has a K1 value calculated by Equation 1below in a range of 0.9 to 1.1:K1=R1(450)/R1(650)+0.044×exp(0.43×bs)  [Equation 1] wherein, bs is asingle color of the polarizing plate, R1 (450) is a reflectance (unit:%) of the polarizing plate for light having a wavelength of 450 nmmeasured under a state where the polarizing plate is positioned on areflective surface having a reflectance of 23% for light having awavelength of 550 nm, and R1 (650) is a reflectance (unit:%) of thepolarizing plate for light having a wavelength of 650 nm measured undera state where the polarizing plate is positioned on a reflective surfacehaving a reflectance of 23% for light having a wavelength of 550 nm, andfurther satisfying at least one condition of the following conditions 1to 4 and at least two conditions of Conditions 1 to 3: Condition 1: a −avalue of 2 or less in CIE Lab color space; Condition 2: a b value of 4or less in CIE Lab color space; Condition 3: a ratio (−b/a) of −a valueand b value of 2.5 or less in CIE Lab color space; Condition 4: a −bcvalue of 0.05 to 40 in CIE Lab color space; and wherein the polarizingplate has a polarizer comprising a PVA-based film and an anisotropicabsorbent material adsorbed and oriented on the PVA-based film.